Apply the Liskov substitution principle to OutputDevice::GetBackgroundColor().
This helps in SmTmpDevice::Impl_GetColor() because it no longer needs to know
about what type of OutputDevice it is calling to get the background color.
This forced a rename of basctl::ModulWindowLayout::GetBackgroundColor() to be
GetSyntaxBackgroundColor(), but this is a happy coincidence as it makes the
function intent clearer anyway.
Change-Id: I11298a63cb01c187f3a8a4a2c9e90eacda6c3e6b
Reviewed-on: https://gerrit.libreoffice.org/75521
Tested-by: Jenkins
Reviewed-by: Tomaž Vajngerl <quikee@gmail.com>
Chris Sherlock
41dbf08b99